Instead of adding the trial arm to an ongoing US process, a new study would be run to evaluate a lower dosage that performed better than a full amount in AstraZeneca's studies, Soriot said in a Bloomberg News report.
"Now that we've found what looks like a better efficacy we have to validate this, so we need to do an additional study", AstraZeneca boss Soriot told Bloomberg.
The recent information shows that the 90% effective dose of the drug was based on a half-dose, then followed a month later with a full dose.
The additional trial was not likely to delay regulatory approval in Britain and the European Union, AstraZeneca chief executive Pascal Soriot said.
Gillies O'Bryan-Tear, from the UK Faculty of Pharmaceutical Medicine, said "the eventual efficacy rate may change" but "the validity of the low dose/high dose group results are unlikely to be questioned".More news: Xiaomi Shows Strong Growth Momentum in Q3 2020 Financial Report
"This foundation for the allocation process will help us mitigate the spread of Covid-19 in our communities, protect the most vulnerable Texans, and safeguard crucial state resources", he added.
"This would add to data from existing trials which are now being prepared for regulatory submission".
When clinical trials for this vaccine revealed results on Monday, it appeared to be either 90% or 62% effective at treating COVID-19.
"This was reviewed by the independent Data Safety Monitoring Board and the United Kingdom regulator, both of whom approved the continuation of this dosing regimen and the regulator publicly confirmed that there was "no concern". That said, this could extend the amount of time that it takes for the Oxford vaccine to be approved in the USA, since this will proceed ahead of a planned US trial that would be required for the FDA to approve it for use domestically. Authorization in some countries is still expected before the end of the year, he said.
Earlier this week, it was reported that the Covid-19 vaccine developed by Oxford University and AstraZeneca shows an average 70 per cent effectiveness in preventing those vaccinated from falling ill with the virus. This was because some of the vials used in the trial didn't have the right concentration of vaccine.More news: North Yorkshire to go into Tier 2 after lockdown
"More data will continue to accumulate and additional analysis will be conducted refining the efficacy reading and establishing the duration of protection", the spokesperson said.
Even so, the AstraZeneca shot developed with Oxford University is cheaper to make, easier to distribute and faster to scale up than its rivals.
Oxford's communications manager for vaccines told CNN on Wednesday that "dose selection for any new vaccine is a complicated area, and in exploring methods of dose selection, we discovered one gave a lower dose than expected".
He said regulators were informed immediately and agreed to continued testing of the vaccine in different measures.
He added: "The variety of age groups and dosing regimes is a feature of a number of the vaccine trials and not just the Oxford AstraZeneca vaccine".More news: Public alerting system test to take place Wednesday